Control Valve Types: Classification & Advantages

Each and every different control valve type has been designed with a specific purpose in mind. In this article, you&#;ll read about different types and categories of Valves to get a better understanding of its internal parts and units. Read on and see how Linquip eliminates the need for you to search more on this subject.

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The Final Goal of Different Control Valve Types

The final control element or the control valve can convert the control signal of the controller with the help of a pneumatic device and regulate the fluid flow in the system. They can be used for different liquids, gasses, steam, air, etc.

Classification of Control Valve Types

Control valves can be categorized based on different features and control valve traits. Some prefer to categorize them based on control valve parts as well. The main categorizations are according to the movement profile of the controlling element, functionality, actuating medium, and pressure drop profile.

1. Pressure Drop Profile

   • High-Recovery Valve (e.g. Butterfly valve, Plug valve, Gate valve, Ball valve, etc.)
   • Low-Recovery Valve (e.g. Angle valve, Globe valve, etc.)

2. Functionality

   • Check Valve (e.g. Turbine bypass valve, etc.)
   • Shut-off and on-off Valve (e.g. Gate valve, Pinch valve, etc.)
   • Spring-Loaded Safety Valve

3. Actuating Medium

• Manual Valve
• Pneumatic Valve
• Hydraulic Valve

4. Movement Profile of the Controlling Element

• Linear Motion (e.g. Gate, Globe, Diaphragm, etc.)
• Rotary Motion (e.g. Ball, Butterfly, Plug, etc.)

The most common classification is based on motion and we&#;ll briefly talk about its subcategories.

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A. Linear Motion

Linear Motion Valves are named because of their closure member&#;s shape. A closure member in these control valve types moves with a linear motion resulting in the modifying the rate of flow through the valve.

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1. Gate Valves

   These valves are suitable for conditions with high temperature and are used for on/off applications and non-throttling services. This is because of their design which can be either fully open or fully closed. Gate valves have a sliding gate which moves by the stem to handle the flow. Gate valves best work when a straight-line flow of liquid is required with minimum restriction.

   They are further divided into two subcategories: Parallel and Wedge-Shaped. The closure member in this type of valve is a flat face, a vertical disc, or a sliding gate. When you rotate the stem in a CTC (clockwise to close) motion or a CTO (clockwise to open) motion, gate valves begin to operate. With the movement of the stem, the gate moves up / down on the threaded step. With several turns of the valve, it goes from fully open to fully close. These valves are popular because of their tight sealing. And they also have a low pressure drop when they fully open. One of the disadvantages of Gate Valves is that they require large actuating force. Not to mention their slow response characteristics.

2. Globe Valve

   Disc or plug in Globe valves moves on or off the seat. The opening of the seat is proportional to the plug&#;s travel. This control valve type is used for throttling purposes. They are among linear motion valves and can start, stop, and regulate the flow. The closure in globe valves is initiated with the help of a plug that has a flat or convex bottom, lowered onto a horizontal seat. This seat is in the center of the globe valve.

   Globe valves are faster to open or close and have a reliable form of seating. The down point is that the seat disc in such valves wears in partial open conditions.

3. Diaphragm Valve

   The closure member in the diaphragm valve is a compressor connected to the flex diaphragm. When the valve is open, the diaphragm is lifted and the fluid flows and when it is closed, the diaphragm closes the flow path tightly.

   Diaphragm valves are suitable for corrosive liquids at low temperature and pressure. The simplicity of the construction and easy maintenance are among the advantages of using diaphragm valves. But keep in mind that you can&#;t use them in environments with high temperature and high pressure.

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B. Rotary Motion:

The closure member in Rotary valves modifies the rate of the flow through the valve with a rotary motion. Plug valves, Ball valves, and Butterfly valves are among the popular rotary valves.

If you are looking for more details, kindly visit different types of control valves and their applications.

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1. Plug Valve
   The plug in the Plug Valves is cylindrical or tapered, depending on the design. While open, the inlet and outlet ends of the plug valve are connected to each other via the bore in the plug to provide the flow line. Plug valves are suitable for chemical or petrochemical industries providing on/off services. They are also capable of handling fluid containing solids.
   Plug valves are usually small and need less maintenance compared to other control valve types. Plus, they require less headroom due to their small size. Low pressure drop, quick opening and providing tight shut off are among the features you can expect from Plug valves. The disadvantage of these valves is that they&#;re relatively more expensive and are not recommended for throttling action.
2. Ball Valve
   The name of this valve suggests the shape of its closure member that looks like a ball, containing a port for fluid flow.  In the opening position, the ball valve enables a straight-through flow. And with a 90-degree rotation of the ball, the flow stops. Low pressure drop and quarter-turn actuation enable ball valves to be used in shut-off applications. They endure high-temperature as well as high pressure of the environment. This control valve type is also used for pressure and flow control and also for corrosive fluids, slurry, normal liquids and gasses as well. Easy maintenance and low torque are also two other plus points of ball valves. One of the disadvantages of this control valve type is that when the fluid traps in the ball in the closed position, sometimes the vapor pressure builds up and results in corrosion.
3. Butterfly Valve
   Having a circular disc or vane rotating at right angles as the closure member, Butterfly valves enable straight-through fluid flow when in open position. And similar to the ball valves, they stop the flow with a 90-degree rotation. This control valve type in the rotary section is capable of large flow control as well as low-pressure applications. But they should be used where leakage is not important.
   Quick opening, low pressure drop, affordability, compact form, and quick opening are among the advantages of butterfly valves. The only disadvantage of this control valve type is that the shut off is not tight.

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 So, now you know everything you needed to know about different control valve types! Do you think these differences have more effects other than what we mentioned above? Share your thoughts with Linquip in the comment section. And feel free to sign up on our website if you want our experts to answer your most complicated questions regarding this field.

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What is a Control Valve?

A control valve is an imperative component used to regulate fluid flow in many systems. By varying the size of the flow passage following signals from a controller, control valves directly modify the flow rate. They play a critical role in managing process quantities such as pressure, temperature, and liquid level. In the semantics of automatic control, control valves are also known as &#;final control elements&#;.

Control valve types vary widely, and understanding each type, its mechanism, and where it fits best is crucial for many industries. This is helpful not just when making an installation decision, but also for efficient control, operation, and maintenance of the systems they govern.

How Do Control Valves Work?

Control valves operate with the help of a valve actuator, which can be electrical, hydraulic, or pneumatic. It is designed to automatically open or close based on a control signal to modulate the valve. This valve modulation allows for precise control of fluid flow, adjusting the rate to match the specific requirements of an industrial process.

A modulating valve can be set to any position between fully open and fully closed using a valve positioner, ensuring it reaches the desired degree of opening. Pneumatic actuators are typically used as they only require a compressed air supply, providing a straightforward and efficient function.
The valves also follow a communication protocol, often a &#;Smart&#; communication signal added to the usual 4-20 mA control current, giving feedback to the controller regarding the health and status of the valve position. This system greatly enhances the precision and reliability of control valves in industrial settings.

What Are the Components of Control Valves?

Linear Motion Control Valve

Valve body: The valve body in linear control valves contains an opening, and the flow rate is controlled by moving a closure member in and out of this opening. The closure members in linear valves can be of different kinds, such as disks, slides, and more.
Bonnet: This component houses the packing and also acts as a guide to the stem. It provides the stuffing box through which the stem moves and seals the system to prevent any leakage.
Trim: This forms the internal parts of the valve and comes in direct contact with the fluid. It usually consists of the stem, closure member, and seat.

Rotary Motion Control Valve

Rotary motion control valves regulate the flow of fluid through rotating elements, controlling flow by turning these elements 90 degrees.

What Are Some Types of Control Valves?

When it comes to control valve types, they fall into two major categories: linear control valves and rotary control valves. Each of these types comes with various subsets, each with its unique functionalities and applications.

Linear Control Valve

1. Globe Valves: These are named for the globular cavity around their valve seat. Globe valves are an excellent choice for scenarios requiring flow resistance and substantial pressure drops.
2. Diaphragm Valves: These valves use a deforming flexible surface or diaphragm for closure. They find major use in shut-off services of slurries or corrosive fluids.
3. Gate Valves: The flat-faced vertical disc or gate of this valve slides down to block the flow, making it ideal for full open or close operations.

4. Pinch Valves:These operate similar to diaphragm valves but offer a very low pressure drop due to no internal obstructions.

Rotary Control Valve

1. Ball Valves: These have a ball-shaped closure with a port, allowing straight-through flow when open and shutting off flow when turned 90 degrees.

2. Butterfly Valves: These valves use a circular disc or vane for closure, offering low pressure drop and fast operation.
3. Plug Valves: They have a cylindrical or tapered plug as the closure member, allowing straight-through flow when opened.

Control Valve TypeAdvantagesDisadvantagesGlobe ValveExcellent shut off capability. Can be used for throttlingHigh pressure drop, More expensiveBall ValveLower cost, Can handle high flow rates, Quick to open and closePoor throttling capabilities, Not suitable for high temperaturesGate ValveLow pressure drop, Good for on/off serviceNot suitable for throttling, Prone to vibration when partially openButterfly ValveLow cost, Good for large pipe diametersNot as effective for tight shut off, Not suitable for high pressureDiaphragm ValveGood for corrosive and slurry flow, Lower costLimited to lower pressure and temperature applicationsPinch ValveGood for handling slurries, easy maintenanceLimited to low-pressure applicationsPlug ValveGood for high temperature and pressure applications, Offers tight shutoffMore expensive, high torque required to operate

What Factors Should Consider When Installing Different Types of Control Valves?

When planning to install different types of control valves, several crucial considerations come into play:
Fluid Type: Understand the characteristics of the fluid&#;their nature (corrosive, viscous, etc.), temperature, and pressure&#;which will directly impact the valve type selection.
Valve Material: Ensure the materials used in the valve construction are compatible with the fluid used. This is crucial to prevent corrosion, wear, and premature failure.
Flow Control Requirements: Consider the desired flow rate and changes in flow rate required for your process control. Certain control valve types might be better suited for high flow rate applications, while others excel in precise flow control.
Design and Size: The design and size of the valve should match the specifications of your pipeline, ensuring proper fitting and efficient operation.

System Layout: Consider the physical space for the valve installation. Certain types of control valves might require additional room for actuators and maintenance access.
Safety and Regulations: Compliance with safety rules and industry regulations in your specific sector is vital. For instance, control valves used in certain industries or applications might need to adhere to strict safety certifications.

What Are the Applications of Control Valves?

Control valves are versatile devices used across a broad spectrum of industries:
Chemical and Petrochemical Industry: Control valves are used to manage and monitor the flow, temperature, and pressure of various chemicals in the process lines.
Oil and Gas: In refineries and pipelines, control valves manage the flow and pressure of oil and gas during extraction, processing, and transportation stages.

Food and Beverage Industry: To maintain precise control over process variables during the manufacturing process, control valves are used.
Water and Waste Treatment: Flow control valves manage the flow rate of water and waste materials, ensuring efficient operation of the treatment processes.
HVAC Systems: Control valves manage the temperature and pressure within air conditioning systems, enhancing their efficiency and effectiveness.
Power Generation: Control valves play a vital role in managing the flow of steam in power plants, directly impacting operational efficiency.

What to Consider Before Buying Control Valves?

1. Requirements: Identify your operational needs&#;flow rate, pressure, temperature, and valve closure or opening speed.
2. Material Compatibility: Ensure the material of the valve is corrosion-resistant and suits the type of fluid in your system.
3. Valve Size: A valve&#;s size should correspond precisely to the pipeline diameter where it will be installed.
4. Performance Parameters: Consider a valve&#;s hydraulic performance, including pressure drop, flow coefficient (Cv), and rangeability, ensuring the valve efficiency meets your process requirements.
5. Safety: Consider valves with safety features such as automatic failsafe modes (Fail-open or fail-close) for higher risk applications.
6. Maintenance: Opt for valves that are easy to maintain, offering long-term reliability and reducing overall operation costs.
7. Cost: While it&#;s essential to consider the initial cost of a valve, factor in lifetime costs, including operation, maintenance, and potential downtime.

Conclusion

Control valves play a crucial role in fluid handling and control systems. With a variety of types, each offering unique advantages for specific applications, it is important to consider the factors that will affect its performance and longevity. From the type of fluid and operating conditions to safety requirements and cost-effectiveness, every aspect matters when opting for the right control valve.

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At Dombor, we provide a broad range of control valve types for diverse applications. Leveraging our industry-leading expertise, we can help you identify the most suitable control valve for your needs. For an instant quote and assistance in your selection process, reach out to us today.

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